Make A Donation

Bone loss and osteoporosis develop so slowly in most women whose bones test normal at age 65 that many can safely wait as long as 15 years before having a second bone density test, researchers report in a new study.

The study, published in Thursday’s issue of The New England Journal of Medicine, is part of a broad rethinking of how to diagnose and treat the potentially debilitating bone disease that can lead to broken hips and collapsing spines.

A class of drugs, bisphosphonates, which includes Fosamax, have been found to prevent fractures in people with osteoporosis. But medical experts no longer recommend the medicines to prevent osteoporosis itself. They no longer want women to take them indefinitely, and no longer consider bone density measurements the sole defining factor in deciding if a woman needs to be treated.

Now, with the new study, researchers are asking whether frequent bone density measurements even make sense for the majority of older women whose bone density is not near a danger zone on initial tests, recommended at age 65.

“Bone density testing has been oversold,” said Steven Cummings, the study’s principal investigator and an emeritus professor of medical epidemiology and biostatistics at the University of California, San Francisco.

The study followed nearly 5,000 women ages 67 and older for more than a decade. The women had a bone density test when they entered the study and did not have osteoporosis. (In a separate national study by the Centers for Disease Control and Prevention, about 70 percent of women over age 65 did not have osteoporosis.)

The researchers report that fewer than 1 percent of women with normal bone density when they entered the study, and fewer than 5 percent with mildly low bone density, developed osteoporosis in the ensuing 15 years. But of those with substantially low bone density at the study’s start, close to the cutoff point for osteoporosis of fewer than 2.5 standard deviations from the reference level, 10 percent progressed to osteoporosis in about a year.

Dr. Margaret Gourlay, the study’s lead author and a family practice specialist and osteoporosis researcher at the University of North Carolina, said she and her colleagues were surprised by how slowly osteoporosis progressed in women.

Medicare pays for a bone density test every two years and many doctors have assumed that is the ideal interval, although national guidelines recommend them only at “regular intervals.”

“I think this will change the way doctors think about screening,” Dr. Gourlay said.

The results, said Joan A. McGowan, director of the division of musculoskeletal diseases at the National Institute of Arthritis and Musculoskeletal and Skin Diseases, “provide telling evidence that you are not going to fall off a cliff if you have normal bone density in your 60s or early 70s, that you are not going to have osteoporosis in the next five years unless something else happens.”

For example, said Dr. McGowan, who was not involved in the study, a woman who had to take high doses of corticosteroids for another medical condition would lose bone rapidly. But the findings “cover most normal women,” she said.

Bone density screening took off after Fosamax, the first bisphosphonate, was approved at the end of 1995. For the first time, doctors had a specific treatment that had been shown to prevent fractures in people with osteoporosis.

For years doctors were overly enthusiastic, prescribing it for women whose bone density was lower than normal but not in a danger zone, keeping women on the drug indefinitely. They even gave a name, osteopenia, to lower than normal bone density, although it was not clear it had real clinical significance.

Now, osteoporosis experts consider osteopenia to be a risk factor, not a disease, and its importance varies depending on a patient’s age, said Dr. Ethel S. Siris, an osteoporosis researcher at Columbia University who was not involved in the study.

Doctors are more likely to prescribe bisphosphonates for older patients and recommend against them for most younger postmenopausal women with osteopenia.

The experts also generally recommend that most people on bisphosphonates take them for just five years at a time, followed by a drug holiday of undetermined length. The idea is to reduce the risk of rare but serious side effects, including unusual thighbone fractures and loss of bone in the jaw.

A risk calculator, FRAX, can help determine whether treatment is recommended. It assesses a combination of risk factors: whether a parent has had a hip fracture, the age of the patient, steroid use, bone density at the hip, and whether the person has broken a bone after age 50, an especially important indicator. Nearly half who break a hip already had already broken another bone, Dr. Siris said.

“If you are an older individual, a man or a woman, who already broke a major bone — spine, hip, shoulder, or pelvis or wrist — take it very seriously and get treated,” she said. “If you have relatively good bone density then you are not at risk now.”